NUTRITION – Preventing Fatigue

Preventing Fatigue During Long Workouts

Gillian Woodward

Preventing fatigue is the number one concern of active people who exercise for more than an hour. This article can help you enjoy high energy and enhanced stamina during long, hard exercise sessions, whether they are in training or in orienteering competition.

TO prevent fatigue during extensive exercise that lasts for more than 60 to 90 minutes, you have two major nutrition goals:

1. to prevent dehydration and 2. to prevent your blood sugar from dropping.

Both dehydration and low blood glucose levels can leave you feeling tired, washed out and can have a considerable effect on your concentration and performance. Here are some tips to help you reach these goals.

Fluid replacement

When you exercise hard, you sweat. Sweating is the body’s way of dissipating heat and maintaining a constant internal temperature. When you sweat for more than an hour, you lose significant amounts of water from your blood. This hopefully triggers the thirst mechanism and increases your desire to drink. Unfortunately for athletes, this thirst mechanism can be an unreliable signal, so you should plan to drink before you are thirsty. By the time your brain signals thirst, you may have lost one percent of your body weight, (the equivalent of 0.5-1 kg of sweat for a 70kg person). This onepercent loss corresponds with the need for your heart to beat an additional 3 to 5 times per minute, hence contributing to early fatigue.

Thirst sensations change with age and older people, even athletes, become less sensitive to thirst. Older people, in particular, should carefully monitor their fluid intake. Light colored urine, in significant volume, is a sign of adequate hydration. Most athletes voluntarily replace less than half of sweat losses. Thirst can be blunted by exercise or overridden by the mind. For safety, always drink enough to quench your thirst, plus at least another 1/3 to a 1/2 as much again.

If you know how much you sweat, you can then replace those losses according to a plan. To learn your sweat rate (and fluid targets), weigh yourself naked before and after a workout. For every kilogram you lose, you should strive to replace up to about 8001000 ml while exercising. This requires training your gut to handle the volume. It is best to try drinking 150 ml every 10-15 minutes. Wearing a platypus bladder on your back and sipping during the workout would be an excellent way to train.

Some people find it helpful set an alarm wristwatch to remind them to drink on schedule. You’ll also need to plan on having the right quantity of enjoyable fluids readily available. Be prepared before your workout. Bring with you the sports drinks and fluids that will enhance your efforts – the ones you like the taste of and are familiar with from training.

Carbohydrates and Blood Sugar

You can significantly increase your stamina by consuming a preexercise snack (1-2 hours prior) that provides fuel for the first hour of the workout and by drinking adequate fluids during exercise. The third trick to enhancing endurance is to consume carbohydrates after an hour of exercise. Depending on your body size and ability to tolerate fuel while you workout, you’ll want to target around 1 gram of carbohydrates per kilogram of body weight per hour of endurance exercise. For example, if you weigh 70kg, you should target about 70 grams per hour, or for a 50 kg person, only 50 grams per hour.

Drinking this carbohydrate in the form of a sports drink is one of the easiest ways to obtain the fuel. Many sports drinks are about 7% sugar solutions, so you can get 7 grams of carbohydrate per 100 ml. To get 50 grams of carbs you would therefore need to drink about 700 ml over an hour, preferably in about 5 slurps of about 150 ml each. During a moderate to hard endurance workout, carbohydrates supply about 50 percent of the energy. As you deplete carbohydrates from muscle glycogen stores, you increasingly rely on the carbs (sugar) in your blood for energy. By consuming carbohydrates such as sports drinks, bananas, or energy bars during exercise, you can both fuel your muscles as well as maintain a normal blood sugar level. Because your brain relies on the sugar in your blood for energy, keeping your brain fed helps you think clearly, concentrate well, and remain focused. So much of performance depends on mental stamina, especially in a sport like Orienteering, where you are constantly making decisions and planning your next leg. Maintaining a normal blood sugar level is essential to optimize your performance and boost your stamina. Your body doesn’t care if you ingest solid or liquid carbohydrates – both are equally effective forms of fuel. But you just have to learn which sports snacks settle best for your own body – sports drinks, gels, jelly snakes, breakfast bars, dried figs or dates, defizzed soft drink, whatever you find the easiest to digest. You’ll learn through trial and error which snacks help prevent fatigue, boost performance and contribute to enjoyment of your long, hard workouts. Despite popular belief, sugars (in the foods/drinks mentioned above) can be a positive snack during exercise and are unlikely to cause you to “crash” (experience hypoglycemia or low blood glucose levels). That’s because sugar feedings during exercise result in only small increases in both insulin and blood glucose. Yet, too much sugar or food taken at once can slow the rate at which fluids leave the stomach. Hence, “more” is not always better. So work out the right amount for you – practice using it in training, so you are well prepared for competition in longer events. Keep your brain and body well fuelled !